1. Field of the Invention.
The present invention is broadly concerned with an improved compact smoke generator apparatus used for wind tunnel testing. More particularly, it is concerned with a smoke generator device which is improved by provision of a compact, smoke generator tube which is either wire-packed or crimped to certain critical dimensions and in operation produces an uninterrupted flow of smoke.
2. Description of the Prior Art.
A wide variety of smoke generating devices are available in the field of wind tunnel research directed to airflow studies. Such research is typically of the type making use of wind tunnels to determine airflow patterns around scale models, and has thus generated a need for smoke generation devices that are compact and inexpensive. In addition to being compact, such smoke generating devices must also be equipped with sufficient smoke generating capacity to provide visible indication of airflow over a model being tested.
Because of the compact size of such equipment, however, the characteristics of the flow of heat and fluid through the compact equipment are such that resultant smoke discharge is intermittent rather than continuous. This undesirable phenomenon is a persistent problem in the operation of compact smoke generator devices and is sometimes called "puffing". Puffing is believed to be caused by the emission from the smoke generator device of a saturated liquid/gas mixture. (As used herein, the term "smoke" means a vaporized fluid having the appearance of smoke.) In other words, such compact devices often fail to produce a continuous stream superheated vapor (i.e., devoid of liquid) due to inadequate heat transfer and fluid flow characteristics associated with the device.
If puffing occurs during operation of the smoke-generating device, then an additional problem is typically experienced in that some of the liquid entrained in the liquid/gas discharge mixture will be deposited in the form of droplets on the surface of the model being tested in the wind tunnel. Droplet formation on model surfaces during testing tends to distort the airflow over the surface.
In use, if the discharge from a smoke generator is intermittent, or if the smoke discharge causes the formation of liquid droplets on the model surface, the flow characteristics of air over the surface of a scale model cannot be reliably determined. Accordingly, the requirements for a successful, efficient and compact smoke-generating apparatus are relatively stringent with one of the most troublesome difficulties being the emission of intermittent streams of smoke during periods of use.